PURPOSE: To surely turn OFF an LED lamp when an AC power source is turned ON and a three-pole bi-directional thyristor is turned OFF by connecting resistors in parallel at the input side of a diode bridge circuit rectifying an alternative current to a direct current.

CONSTITUTION: A light emitting diode LED display element 31 is connected with a series circuit connected, for example, four LED lamps 33 in series via a current-limiting resistor 36 at the input side of the diode bridge circuit 35, while a shunt resistor 37 is connected at the input side of the diode bridge circuit 35 in parallel. When both an AC power source 41 and a triac 42 are turned ON, an AC current is made to flow through the diode bridge circuit 35 and is made to rectify and then each LED lamp 33 is turned ON with a current value properly controlled with the current-limiting resistor 36. On the other hand, when the AC power source 41 is turned ON and the triac 42 is turned OFF, a portion of a minute leakage current leaking from the triac 42 flows in the shunt resistor 37 and a minute current flowing in the diode bridge circuit 35 is decreased and each LED lamp 33 is turned OFF.